1. Field of the Invention
The present invention is directed to an x-ray examination positioning apparatus of the type having a base and an arm with a first end which is rotatable around a first shaft or axle attached in the base and a second end which is connected to a holder in which a curved carrier is displaceably arranged, with an x-ray source mounted at one end of the carrier opposite an x-ray receptor mounted at the other end of the carrier.
2. Description of the Prior Art
An examination table that is displaceable at least in its longitudinal direction is employed in conjunction with x-ray examinations with a positioning apparatus of the aforementioned type. Given, for example, cardiac examinations, it is a great advantage that the curved carrier of the positioner, maintaining its isocenter, can be brought from a position wherein the carrier is in a vertical position behind the head and of the table and wherein the head end is placed between the x-ray tube and the receptor, into a lateral position wherein the carrier is perpendicularly arranged in a vertical position compared to the imaginary center axis of the examination table. Another important advantage is that the carrier, in the described lateral position, can be displaced into another lateral position wherein the central ray of the x-ray tube or of the receptor proceeds in a horizontal plane. Another advantage is that the positioner is fashioned such that the team of physicians has good access to the patient.
An x-ray examination positioning apparatus of the type initially cited is described in the brochure "Advantx L/C" of the GE Medical Systems. The base of the positioner is connected to an L-shaped arm having one leg proceeding along the floor. The axis of the fastening device, around which the arm and the base are rotatable, is attached to the floor below the head end of the examination table. The holder, wherein the carrier for the x-ray tube and the receptor is displaceably arranged, is rigidly connected to an upright leg of the arm. As a result of the leg that extends under the table and as a result of the fastening means, the positioner together with the carrier for the x-ray tube and the receptor can be rotated from a position wherein the carrier is attached to the head end of the table into a further position wherein the carrier is arranged at an angle of 90.degree. relative to the longitudinal direction of the table. The positioner is also constructed such that the center line between the x-ray tube and the receptor is in axial alignment with the axis of the fastening means given a vertical setting. This is achieved by the x-ray tube and the receptor being connected to the carrier via a boom. As a result, the x-ray tube and the receptor are always rotated around the same point when rotating the positioner around the axis of the fastening device. Since the arm at the floor in the area of the axis of the fastening device is comparatively wide and high, however, the physician may accidentally hit the floor arm with his or her feet during the examination, this being potentially disturbing. Due to the position and thickness of the arm, the carrier for the x-ray tube and the receptor cannot be lowered down to the floor given a vertical attitude. Given such a vertical attitude, the lowering of the x-ray tube and of the receptor by 4 through 5 cm, which is approximately the thickness of the arm, can be critical in order to obtain a good working height for the team of physicians. A further disadvantage is that the carrier can be turned into a lateral position only .+-.45.degree.. A lateral position is achieved only in combination with a head position. The inside dimension of the curved carrier determines how far the x-ray tube can sweep when the head end of the table is placed within the carrier maximally close to the holder. This is a limitation of the setting possibilities of the x-ray tube and of the receptor. This known positioner, moreover, is relative complicated in terms of structure and the floor arm, the fastening device and the boom of the x-ray tube and of the receptor limit access to the patient.
European Application 0 386 842 discloses an x-ray examination positioner having a base firmly connected to the floor, an L-shaped arm arranged at the base and rotatable around a shaft, and a carrier for an x-ray tube and a receptor arranged at the free end of the arm. The carrier is rotatably secured directly to the arm via an axle. As a result of this structure, the imaginary axle extensions as well as the central ray between the x-ray tube and the receptor intersect in a common point. Because the carrier for the x-ray tube and the receptor, however, is rotatably attached directly to the arm, the positioner exhibits certain limitations in terms of its motion pattern. Thus, for example, the carrier cannot be shifted into what is referred to as a head-placed attitude that has just been described. In an exemplary embodiment described in said European Application, a holder for an arcuate carrier is provided that is firmly connected to the free end side of the arm such that the holder and the carrier form an extension of the arm. In order to compensate the L-shaped arm such that the imaginary extension of the base axle intersects the central ray of the x-ray tube and of the receptor, the x-ray tube and the receptor are connected to the carrier via booms. As a result of this structure, the carrier cannot undertake a spherical movement around a desired point. The carrier also cannot assume a lateral position that is perpendicular in relationship to the examination table, since the arm together with the carrier proceeds parallel to the examination table in all attitudes.